Raman spectra of gases. XVIII. Internal rotational motions in ethylamine and ethylamine-d$sub 2$
The Raman spectra of gaseous CH$sub 3$CH$sub 2$NH$sub 2$ and CH$sub 3$CH$sub 2$ND$sub 2$ have been recorded from 100 to 600 cm$sup -1$. Both ground and excited states of the methyl and amino torsional modes for the gauche conformer have been observed. The overtone of the methyl torsion has also been observed for the gauche conformer. The methyl barriers in the gauche conformers of the CH$sub 3$CH$sub 2$NH$sub 2$ and CH$sub 3$CH$sub 2$ND$sub 2$ molecules were found to be 3.71 +- 0.05 and 3.59 +- 0.05 kcal/mole, respectively. The apparent difference in the barrier heights for these two isotopic species is attributed to a difference in the coupling between the methyl and amino torsions in these two molecules. The potential function for internal rotation around the C--N bond in CH$sub 3$CH$sub 2$ND$sub 2$ was determined and the following potential constants found: V$sub 1$=279 +- 16 cm$sup -1$, V$sub 3$=707 +- 4 cm$sup -1$, V$sub 6$=-12 +- 3 cm$sup -1$. The energy difference between the potential energy minima of the gauche and trans conformations is 207 cm$sup -1$ (0.592 kcal/mole) with the trans being the more stable. The calculated gauche--gauche barrier is 779 cm$sup -1$ (2.23 kcal/mole) and the trans--gauche barrier is 572 cm$sup -1$ (1.64 kcal/ mole). A similar potential function was determined for the CH$sub 3$CH$sub 2$NH$sub 2$ isomer but the fit to this one-dimensional model was not as good as that obtained for the deuterium compound probably because of thegreater coupling in the light molecule. (AIP)
- Research Organization:
- Department of Chemistry, University of South Carolina, Columbia, South Carolina 29208
- NSA Number:
- NSA-33-008882
- OSTI ID:
- 4127507
- Journal Information:
- J. Chem. Phys., v. 63, no. 10, pp. 4110-4113, Other Information: Orig. Receipt Date: 30-JUN-76
- Country of Publication:
- United States
- Language:
- English
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